Hot air heater

ABSTRACT

A hot air heater has a housing having formed therein an inlet port for sucking room air and an outlet port. A circulation fan, a burner, and a heat exchanger which causes to flow combustion gas from the burner through an inside of the heat exchanger are housed in the housing. The room air sucked by operation of the circulation fan into the inlet port is heated by the heat exchanger for blowing forward as hot air out of the outlet port. A supporting plate is disposed to support the heat exchanger inside the housing. In order to limit the temperature increase in the housing by heat transmission through the supporting plate, and in order to improve the thermal efficiency, the supporting plate is provided with radiating fins. Preferably, the radiating fins are made up of cut-and-raised pieces formed in the supporting plate.

This application claims priority under 35 U.S.C. §119 to Japanese PatentApplication No. 2009-206672, filed Sep. 8, 2009, which is incorporatedby reference.

BACKGROUND

1. Technical Field

The present invention relates to a hot air heater (or forced flueheater) that heats the room air by combustion gas from a burner througha heat exchanger.

2. Related Art

As this kind of hot air heater, there is known one having the followingconstruction. Within a housing having formed therein an inlet port forsucking room air and an outlet port, there are housed a circulation fan,a burner, and a heat exchanger which is arranged to cause to flowcombustion gas (or flue gas) from the burner through an inside of theheat exchanger. The air sucked from the inlet port by the operation ofthe circulation fan is heated by the heat exchanger and is blown out ofthe outlet port as hot air (see, e.g., Patent Document 1).

Although not disclosed in Patent Document 1, this kind of hot air heateris provided with a supporting plate for supporting the heat exchangerinside the housing. The supporting plate is ordinarily constituted by asimple plate member and is generally fixed to the inside of the housingby means of screws.

It is, however, to be noted that the heat exchanger, when a fuel isburned in the burner, will reach a relatively high temperature. The heatfrom the heat exchanger will be transmitted through the supporting plateto that part of the housing to which the supporting plate is fixed byscrewing, with the result that such a part will reach a hightemperature.

Patent Document 1: JP-A-2003-121004

SUMMARY

In view of the above problems, it is an advantage of the invention toprovide a hot air heater in which the temperature increase in thehousing by heat transmission through the supporting plate can be limitedand in which the thermal efficiency can be improved.

In order to solve the above-mentioned problems, this invention is a hotair heater comprising: a housing having formed therein an inlet port forsucking room air and an outlet port; a circulation fan, a burner, and aheat exchanger, all being housed in the housing. The heat exchanger isarranged to cause combustion gas from the burner to flow through aninside of the heat exchanger so that the room air sucked by operatingthe circulation fan into the inlet port is heated by the heat exchangerfor blowing forward as hot air out of the outlet port. In theabove-mentioned hot air heater, a supporting plate is disposed tosupport the heat exchanger inside the housing, and the supporting plateis provided with a radiating fin.

According to the invention, the heat that is transmitted from the heatexchanger to the supporting plate is radiated from the radiating fin.The amount of heat to be transmitted to the housing through thesupporting plate is reduced and, consequently, the temperature increasein the housing can be limited. At the same time, since the air flowingaround the supporting plate gets heated by the heat radiation from theradiating fin, the thermal efficiency is improved.

Preferably, the radiating fin is disposed such that a plate surface ofthe fin obliquely crosses the direction of flow of the air from thecirculation fan. According to this arrangement, the heat exchangebetween the radiating fin and the flow of the air is performedefficiently. As a result, the reduction in the amount of heat transferto the housing and also the heating of the air can be accelerated.

In this invention, preferably, the radiating fin is made up of acut-and-raised piece formed in the supporting plate. According to thisarrangement, unlike a case in which a radiating fin in the form of amember separate from the supporting plate is fixed to the supportingplate, the cost can be reduced by minimizing the number of constituentparts. Further, the opening that is formed by the cut-and-raised pieceof the radiating fin contributes to the reduction in the heat transferarea of the supporting plate. Consequently, the amount of heat transferto the housing can further reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings in which:

FIG. 1 is a perspective view of a hot air heater according to anembodiment of this invention;

FIG. 2 is a sectional side view of the hot air heater according to theembodiment of this invention;

FIG. 3 is a sectional front view taken along the line III-III in FIG. 2;

FIG. 4 is an enlarged plan view, partly shown in section, of a main parttaken along the line IV-IV in FIG. 3; and

FIG. 5 is a perspective view of a main part of the hot air heateraccording to an embodiment of this invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

With reference to FIGS. 1 through 3, reference numeral 1 denotes ahousing of a hot air heater according to an embodiment of thisinvention. The housing 1 is made up of: a main body constituted by arear plate part 11, a right-side side-plate part 12 and a left-sideside-plate part 12, a top plate part 13, and a bottom plate part 14; anda front panel 15 which covers the front surface of the main body. Thereare formed, on an upper portion of the rear plate part 11, an inlet portla for sucking the room air and, on a lower part of the front panel 15,an outlet port lb.

On the top plate part 13 of the housing 1 there is provided an operationpanel 16. Further, on an outer surface of the rear plate part 11 of thehousing 1, there is disposed a guard frame 17 which encloses the pipingspace among a supply and exhaust duct (not illustrated) which extendsoutdoors, an exhaust pipe 53, and a combustion fan 6.

At an upper inside portion of the housing 1 there is housed acirculation fan 2. The circulation fan 2 is disposed inside a fan casing21 which faces the inlet port 1 a, and is constituted by an oblong crossflow fan driven by a motor 22.

Inside the housing 1 there is defined an air passage 3 which connectsthe fan casing 21 and the outlet port 1 b together. The air passage 3 isenclosed by: the rear plate part 11; a first lateral partition plate 31which is disposed on the inside of the left-side side-plate part 12(left as seen in FIG. 3); a second lateral partition plate 32 whichextends downward from the right end part, as seen in FIG. 3, of the fancasing 21; a lower partition plate 33 which is disposed slightly belowthe lower end of the outlet port 1 b; and a front partition plate 34which extends downward from the front edge of the fan casing 21.

Inside the housing 1 there is further housed a cylindrical burner 4which is supplied with a fuel gas through a gas valve unit 41 and a pipe42 connected thereto, the burner 4 being housed in a manner to passthrough a lower part of the second lateral partition plate 32. There isalso housed a heat exchanger 5 which is positioned inside the airpassage 3 and which causes the combustion gas (flue gas) of the burner 4to flow through the inside. It is thus so arranged that the room airsucked from the inlet port 1 a by operating the circulation fan 2 isheated by the heat exchanger 5 and is blown out of the outlet port 1 binto the room as hot air.

Inside the housing 1 there is also housed a combustion fan 6 whichsupplies the burner 4 with outside air as combustion air through an airsupply duct section of the supply and exhaust duct. The combustion fan 6is constituted by a centrifugal fan which is driven by a motor 62 andwhich is disposed inside a fan casing 61 that is fixed to the rear platepart 11 of the housing 1. In addition, a humidification water reservoir7 to be filled with water is disposed below the lower partition plate33. It is thus so arranged that the hot air is supplied with steamthrough an opening 33 a formed through the lower partition plate 33.That lower end part 15 a of the front panel 15 which lies below theoutlet port 1 b is arranged to be detachable so that the humidificationwater reservoir 7 can be taken out of position for refilling it withwater.

The heat exchanger 5 is provided with: a combustion tube 51 whichextends leftward as seen in FIG. 3 from the burner 4; a bellows-type ofheat exchange tube 52 which is laterally disposed above the combustiontube 51; and an exhaust pipe 53 which is laterally disposed between thecombustion tube 51 and the heat exchange tube 52. The left end of thecombustion tube 51, which corresponds to the downstream end thereof, andthe left end of the heat exchange tube 52, which corresponds to anupstream end thereof, are brought into fluid flow communication witheach other through a box 54. Also, the right end of the heat exchangetube 52, which corresponds to the downstream end thereof, and the rightend of the exhaust pipe 53, which corresponds to the upstream endthereof, are brought into fluid flow communication with each otherthrough a box 55. It is thus so arranged that the combustion gas (fluegas) flows through the combustion tube 51, the box 54, the heat exchangetube 52, and the box 55 into the exhaust pipe 53. The downstream end ofthe exhaust pipe 53 is projected out of the rear surface of the housing1 through the rear plate part 11 and is connected to an exhaust ductpart of the supply and exhaust duct.

The heat exchanger 5 is supported by a supporting plate 8 inside thehousing 1. As shown in FIGS. 4 and 5, this supporting plate 8 has: afront plate part 81 which is fixed with screws 81 a to a fixing part 31a formed by cutting and raising the first lateral partition plate 31;and a side plate part 82 which is bent rearward from laterally inneredge part of the front plate part 81 and which is fixed with screws 82 ato the outside surface of the box 54 of the heat exchanger 5. On alaterally outward edge part of the front plate part 81, there is formed,by bending, a flange part 83 which is intended to close the openingsthat were formed as a result of cutting and raising of the fixing part31 a of the first lateral partition plate 31. On a rear edge part of theside plate part 82, there is formed, by bending, a flange part 84 whichcomes into abutment with the rear plate part 11 of the housing 1. Theflange part 84 is engaged with a hook part 11 a provided in the rearplate part 11 at an engaging hole 84 a that is formed in the flange part84.

With the above-mentioned arrangement as it is, the heat from the heatexchanger 5 will be transmitted through the supporting plate 8 to thefirst lateral partition plate 31 or to the rear plate part 11, with theresult that the housing 1 rises in temperature.

As a solution, in this embodiment, there are disposed a plurality ofradiating fins 85 in the front plate part 81 and in the side plate part82, respectively, of the supporting plate 8. According to thisarrangement, the heat transmitted from the heat exchanger 5 to thesupporting plate 8 is radiated from the radiating fins 85. The amount ofheat to be transmitted to the housing 1 through the supporting plate 8is reduced and, consequently, the temperature rise in the housing 1 canbe limited. At the same time, the air that flows around the supportingplate 8 is heated by radiation from the radiating fins 85. In otherwords, the supporting plate 8 functions efficiently as a heat exchangemember, and the thermal efficiency also improves.

Each of the radiating fins 85 is disposed in a manner such that theplate surface thereof obliquely crosses the direction of flow of the airfrom the circulation fan 2 (i.e., crosses the vertical direction at aninclination). Therefore, the heat exchange takes place efficientlybetween the radiating fins 85 and the air flow, with the result that thereduction in the amount of heat transfer to the housing 1 and also theheating of the air can be accelerated.

Alternatively, it may be considered to form the radiating fins 85 in aplate member that is separate from the supporting plate 8 and then tofix the radiating fins 85 to the supporting plate 8 by means of welding,and the like. This solution, however, brings about an increase in thenumber of parts and a higher cost.

As a solution, in this embodiment, the radiating fins 85 are constitutedby cut-and-raised pieces that are formed in the supporting plate 8.According to this arrangement, the radiating fins made of separatemembers are not required, and the cost can be reduced. In addition, theheat transmitting area of the supporting plate 8 is narrowed due to thepresence of the holes 85 a that are formed as a result ofcutting-and-raising of the radiating fins 85. Therefore, the amount ofheat transmission to the housing 1 is further reduced, and thetemperature rise in the housing 1 can more effectively be limited.

A description has so far been made of an embodiment of this invention.This invention is, however, not limited to the above-mentionedembodiment. For example, although in the above-mentioned embodiment, theoutdoor air is supplied to the burner 4 as combustion air, it is alsopossible to supply the indoor air to the burner 4 as combustion air.

1. A hot air heater comprising: a housing having formed therein an inletport for sucking room air and an outlet port; and a circulation fan, aburner, and a heat exchanger, all being housed in the housing, the heatexchanger being arranged to cause combustion gas from the burner to flowthrough an inside of the heat exchanger so that the room air sucked byoperating the circulation fan into the inlet port is heated by the heatexchanger for blowing forward as hot air out of the outlet port, whereina supporting plate is disposed to support the heat exchanger inside thehousing and wherein the supporting plate is provided with a radiatingfin.
 2. The hot air heater according to claim 1, wherein the radiatingfin is disposed such that a plate surface of the fin obliquely crossesthe direction of flow of the air from the circulation fan.
 3. The hotair heater according to claim 1, wherein the radiating fin is made up ofa cut-and-raised piece formed in the supporting plate.
 4. The hot airheater according to claim 2, wherein the radiating fin is made up of acut-and-raised piece formed in the supporting plate.